1 /* crypt.h -- base code for crypt/uncrypt ZIPfile
2
3
4 Version 1.01e, February 12th, 2005
5
6 Copyright (C) 1998-2005 Gilles Vollant
7
8 This code is a modified version of crypting code in Infozip distribution
9
10 The encryption/decryption parts of this source code (as opposed to the
11 non-echoing password parts) were originally written in Europe. The
12 whole source package can be freely distributed, including from the USA.
13 (Prior to January 2000, re-export from the US was a violation of US law.)
14
15 This encryption code is a direct transcription of the algorithm from
16 Roger Schlafly, described by Phil Katz in the file appnote.txt. This
17 file (appnote.txt) is distributed with the PKZIP program (even in the
18 version without encryption capabilities).
19
20 If you don't need crypting in your application, just define symbols
21 NOCRYPT and NOUNCRYPT.
22
23 This code support the "Traditional PKWARE Encryption".
24
25 The new AES encryption added on Zip format by Winzip (see the page
26 http://www.winzip.com/aes_info.htm ) and PKWare PKZip 5.x Strong
27 Encryption is not supported.
28 */
29 #define NOCRYPT
30 #define NOUNCRYPT
31
32 #define CRC32(c, b) ((*(pcrc_32_tab + (((int)(c) ^ (b)) & 0xff))) ^ ((c) >> 8))
33
34 /***********************************************************************
35 * Return the next byte in the pseudo-random sequence
36 */
decrypt_byte(unsigned long * pkeys,const unsigned long * pcrc_32_tab)37 static int decrypt_byte(unsigned long* pkeys, const unsigned long* pcrc_32_tab)
38 {
39 unsigned temp; /* POTENTIAL BUG: temp*(temp^1) may overflow in an
40 * unpredictable manner on 16-bit systems; not a problem
41 * with any known compiler so far, though */
42
43 temp = ((unsigned)(*(pkeys + 2)) & 0xffff) | 2;
44 return (int)(((temp * (temp ^ 1)) >> 8) & 0xff);
45 }
46
47 /***********************************************************************
48 * Update the encryption keys with the next byte of plain text
49 */
update_keys(unsigned long * pkeys,const unsigned long * pcrc_32_tab,int c)50 static int update_keys(unsigned long* pkeys, const unsigned long* pcrc_32_tab, int c)
51 {
52 (*(pkeys + 0)) = CRC32((*(pkeys + 0)), c);
53 (*(pkeys + 1)) += (*(pkeys + 0)) & 0xff;
54 (*(pkeys + 1)) = (*(pkeys + 1)) * 134775813L + 1;
55 {
56 register int keyshift = (int)((*(pkeys + 1)) >> 24);
57 (*(pkeys + 2)) = CRC32((*(pkeys + 2)), keyshift);
58 }
59 return c;
60 }
61
62 /***********************************************************************
63 * Initialize the encryption keys and the random header according to
64 * the given password.
65 */
init_keys(const char * passwd,unsigned long * pkeys,const unsigned long * pcrc_32_tab)66 static void init_keys(const char* passwd, unsigned long* pkeys, const unsigned long* pcrc_32_tab)
67 {
68 *(pkeys + 0) = 305419896L;
69 *(pkeys + 1) = 591751049L;
70 *(pkeys + 2) = 878082192L;
71 while (*passwd != '\0')
72 {
73 update_keys(pkeys, pcrc_32_tab, (int)*passwd);
74 passwd++;
75 }
76 }
77
78 #define zdecode(pkeys, pcrc_32_tab, c) \
79 (update_keys(pkeys, pcrc_32_tab, c ^= decrypt_byte(pkeys, pcrc_32_tab)))
80
81 #define zencode(pkeys, pcrc_32_tab, c, t) \
82 (t = decrypt_byte(pkeys, pcrc_32_tab), update_keys(pkeys, pcrc_32_tab, c), t ^ (c))
83
84 #ifdef INCLUDECRYPTINGCODE_IFCRYPTALLOWED
85
86 #define RAND_HEAD_LEN 12
87 /* "last resort" source for second part of crypt seed pattern */
88 #ifndef ZCR_SEED2
89 #define ZCR_SEED2 3141592654UL /* use PI as default pattern */
90 #endif
91
crypthead(const char * passwd,unsigned char * buf,int bufSize,unsigned long * pkeys,const unsigned long * pcrc_32_tab,unsigned long crcForCrypting)92 static int crypthead(const char* passwd, /* password string */
93 unsigned char* buf, /* where to write header */
94 int bufSize,
95 unsigned long* pkeys,
96 const unsigned long* pcrc_32_tab,
97 unsigned long crcForCrypting)
98 {
99 int n; /* index in random header */
100 int t; /* temporary */
101 int c; /* random byte */
102 unsigned char header[RAND_HEAD_LEN - 2]; /* random header */
103 static unsigned calls = 0; /* ensure different random header each time */
104
105 if (bufSize < RAND_HEAD_LEN)
106 return 0;
107
108 /* First generate RAND_HEAD_LEN-2 random bytes. We encrypt the
109 * output of rand() to get less predictability, since rand() is
110 * often poorly implemented.
111 */
112 if (++calls == 1)
113 {
114 srand((unsigned)(time(NULL) ^ ZCR_SEED2));
115 }
116 init_keys(passwd, pkeys, pcrc_32_tab);
117 for (n = 0; n < RAND_HEAD_LEN - 2; n++)
118 {
119 c = (rand() >> 7) & 0xff;
120 header[n] = (unsigned char)zencode(pkeys, pcrc_32_tab, c, t);
121 }
122 /* Encrypt random header (last two bytes is high word of crc) */
123 init_keys(passwd, pkeys, pcrc_32_tab);
124 for (n = 0; n < RAND_HEAD_LEN - 2; n++)
125 {
126 buf[n] = (unsigned char)zencode(pkeys, pcrc_32_tab, header[n], t);
127 }
128 buf[n++] = (unsigned char)zencode(pkeys, pcrc_32_tab, (int)(crcForCrypting >> 16) & 0xff, t);
129 buf[n++] = (unsigned char)zencode(pkeys, pcrc_32_tab, (int)(crcForCrypting >> 24) & 0xff, t);
130 return n;
131 }
132
133 #endif
134